Additional Inherent in security systems is the problem of false alarms. In situations where local authorities are notified of alarms, false alarms can result in the owner of the system being subject to significant fines. In addition, false alarms waste the limited resources available to the authorities to respond to legitimate alarm situations. It is therefore desirable that a security system permits verification of detected alarm conditions.
Conventional security systems typically protect a building using make/break contacts strategically placed at doors, windows, and other potential entry points. Sensors are installed on doors and/or windows. Motion sensors are installed in strategic areas inside the home. Other devices such as glass breakage detectors, panic or medical alert buttons, low temperature and flood sensors can be installed as well. When the system is on and a sensor is tripped, a signal is sent through a wire, or using radio frequencies (on wireless systems), to the main controller which sounds a siren and dials out via telephone or cellular service to the monitoring station whenever an alarm occurs.
When a contact is broken and an alarm is sounded or relayed to a central control station located within the building, nearby to the building, or remotely to a central control station of the security company. Besides make/break sensors, security companies also use P.I.R. (passive infrared) sensors which sense heat differences caused by animate objects such as humans or animals. Also used are vibration sensors which, when placed upon a window for example, detect when the window is broken, and radio frequency (rf), radar, and microwave sensors, as well as laser sensing. As with the make/break sensors, when any one of the sensors indicates a detection, a system alarm is indicated. A trouble indication is also given if an alarm unit for the building to which the sensors are connected senses that a path to a sensor is interrupted or broken.
With many current alarm systems, all that the receiver of an alarm, whether at a local or remote central station, knows is that an alarm has occurred. However, the occurrence of an alarm provides no indication as to its cause. Thus, the operator has no other knowledge by which he can determine if an alarm signals the presence of a real intruder, or if it is a false alarm. Sensors may commonly go off during inclement weather (they are sensitive to large electromagnetic fields such as occurring during lightning conditions). Such an erroneous condition is properly referred to as a false alarm. Regardless of why they occur, all false and unwanted alarms detrimentally affect the efficiency and operation of a security system.
Many criteria determine whether or not an alarm condition exists. For example, when a person opens a door monitored by a sensor, a potential alarm condition is created. However, an alarm system typically has a keypad or other coded system control by which, if an appropriate entry is made within a prescribed period of time, signifies that the alarm condition is not to be acted upon. Rather, the entrant is someone authorized to enter the premises. Further, the class of intruder (e.g., human or animal) may be perfectly acceptable in one set of circumstances, but not so in another. The common situation is one where an intruder is a human, and his presence results in an alarm being given.
One technological approach to obtaining such verification is through the use of separate audio monitors operating in concert with separate alarm sensors. U.S. Pat. Nos. 4,591,834 and 4,918,717 are directed to such systems. For example, U.S. Pat. No. 4,591,834 refers to the use of miniature, low-frequency dynamic microphones. Alarm activities noted at the microphones are verified via a separate network of discriminator sensors which comprise geophones. Signal processing techniques are utilized to distinguish alarm activity. Intrusion and discriminator sensors are arranged in known patterns comprised of multiple sensors of each type. U.S. Pat. No. 4,918,717 refers to a system wherein a number of microphones are distributed about a secured premises in relation to other intrusion sensors. Upon detection of an intrusion alarm, the microphones can be manually enabled one at a time from the central station to allow an operator to listen to audio activity in proximity to the sensor alarm.
Another approach is the use of video images to monitor a location. However, in prior art devices these images have been low-resolution, freeze-frame pictures, making it difficult for a viewer to discern what is being shown. In addition, in many prior art devices, the video images may not be received by the monitoring party until several moments have passed after the recorded event has actually taken place likely causing any response to be late and less effective.
An additional problem with some existing security systems is that once a person has left the property, it is common for that person to worry that he or she has forgotten to activate or arm the security system. In addition, such persons may have the desire to monitor the property even in the absence of alarm conditions. Further, a person may have the desire to modify aspects of the security system while they are absent. In prior art systems, it has been necessary to telephone a neighbor to ask them to check on the property and report back to the person.